Compression mount for semiconductor devices, and method

ABSTRACT

A mount for semiconductor laser devices comprises thermally conductive anode and cathode blocks on either side of a semiconductor laser device such as a laser diode. Interposed between at least the anode block and the anode of the semiconductor laser device is a sheet of conformable material with high thermal conductivity such as pyrolytic highly-oriented graphite. In some embodiments, a second sheet of such thermally conductive conformable material is interposed between the cathode of the semiconductor laser device and the cathode block. The semiconductor laser device can be either a single laser diode or a diode bar having a plurality of emitters. A thermally conductive, but electrically insulating, spacer of essentially the same thickness as the laser diode or bar surrounds the diode or bar to prevent mechanical damage while still permitting the conformable material to be maintained in a compressed state.

RELATED APPLICATION

This application claims the benefit of U.S. Patent Application Ser. No.61/528,747, filed Aug. 29, 2011, and U.S. patent application Ser. No.13/476,762, filed May 21, 2012, of which the present application is acontinuation, both of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to methods and apparata for mountingsemiconductor devices, and more particularly relates to methods andapparata for mounting of light-emitting semiconductor devices such aslaser diodes and the like.

BACKGROUND

Light-emitting semiconductor devices have been developed over the pastseveral decades to emit either incoherent light (devices referred to as“LED's”) or coherent light (referred to as “laser diodes” or “diodelasers”.) A common attribute of both LED's and laser diodes is a pair ofelectrically conducting surfaces, serving as the anode and cathode ofthe device, through which an electrical current is passed to generatelight. In devices where a high optical output is desirable (e.g., insome LED lighting applications and especially in high-power laserdiodes), a critical aspect of the device mounting relates to the abilityof such mounting to effectively remove waste heat from the device. Thisis of particular importance where high power, high efficiency and highreliability are desired, since all light-emitting semiconductor devicesexhibit declining electrical-to-optical efficiency as the diodetemperature increases; and ultimately succumb to catastrophic failure ifthe diode temperature continues to rise, either with prolonged emissionor at higher current levels.

Both LED's and laser diodes are of remarkably small size given theamount of light these devices can emit, the amount of power theyconsume, and the amount of heat that they generate. By way of example, asingle laser diode “chip” emitting laser light at 1470 nm (SeminexCorporation, Peabody, Mass.) can readily produce four watts ofcontinuous-wave laser emission with an input current of ten amperes anda voltage drop of about two volts (an input electrical power of 20watts, resulting in an efficiency of 20%). The dimensions of this chipare only 0.5 mm wide by 2.5 mm in length, with a thickness of 0.16 mm.Even more remarkably, the actual laser light is emitted by a very thin,narrow region centered on the anode surface (the so-called “P-side”)that is only 95 microns (0.095 mm) wide and 1 micron in height. This“laser stripe” on the P-side has a surface area of 0.095 mm by 2.5 mm,or 0.24 mm². Since in the above example 80% of the input electricalpower becomes waste heat, the power density on the laser stripe surfaceexceeds an enormous 6,000 watts per square centimeter. This represents asignificant amount of thermal energy that must be efficiently conductedaway from the laser diode to avoid overheating or catastrophic failure.

To maximize the conduction of heat away from a hot surface, theso-called thermal conductivity between the hot surface and the coolercontacting surface must be maximized. Two approaches have generally beenused: either mechanically pressing the heatsink against the hot surface(often with an interface substance such as “thermal grease” placed inbetween the two surfaces); or by bonding the two surfaces together witha solder, or glue such as a high-thermal conductivity epoxy. Themechanical approach has not proved practical with semiconductor devicessuch as laser diodes, for two reasons. First, the laser itself has nocasing or housing, and the laser material is quite brittle. Thus, thepressure necessary to achieve good thermal conductivity using a hardheat sink surface can result in cracking of the semiconductor device,either immediately or during use. Secondly, while thermal grease canhelp achieve high thermal conductivity with a lighter pressure, thegrease tends to migrate toward the optical surfaces of the laser diode,resulting in permanent damage to the laser.

Solder bonding has thus been used more frequently for semiconductordevices such as laser diodes, since it offers good thermal conduction toa heatsink, typically better than an epoxy, without putting directmechanical pressure on the brittle diode material. However, thisapproach has its own inherent drawbacks, especially for laser diodes,which are typically fabricated out of gallium arsenide or indiumphosphide. A simple soldering to a copper heatsink routinely fails dueto the difference in the thermal expansion coefficient between the laserdiode material and the heatsink material. To overcome this problem, moredifficult to fabricate (and expensive) heatsink material must be used,having a comparable thermal expansion coefficient. Because the thermalexpansion coefficient of solder is also not perfectly matched to that ofthe semiconductor, it too places stresses on the laser diode.

A related challenge for soldering is that the laser diode has an outputfacet coating consisting of a partially-transmitting, multilayerdielectric material, and a highly reflective coating on the rear laserfacet. Both of these optical surfaces must be completely undisturbedduring the soldering process, or the laser will likely fail. Thus, manyfluxes that might typically be used to remove oxides during thesoldering process cannot be used.

In addition, it is desirable to subject laser diodes to minimaltemperature rise during soldering, but low melting-point solders such asindium and its alloys do not generally “wet” surfaces as well as highertemperature solders. This requires that the laser diode surface bedesigned to be as “solderable” as possible. Thus the metallization onthe P-side is typically a “sandwich” of vacuum-deposited layersconsisting of for example, a 50-nanometer layer of titanium, followed bya 125-nm layer of platinum, and covered finally with a 250-nm layer ofgold.

Still further, the solder must be in intimate contact with the entirelength of the laser stripe; if it is not, the region without contactbecomes catastrophically hot. Unfortunately, when the optical coating isdeposited onto the output facet of the laser diode chip, some of thecoating material may get inadvertently deposited on the P-side of thechip and prevent the solder from bonding to the chip in that area. Thistypically results in infant failure of the chip. A common reason forrejecting laser chips prior to solder-mounting to a heat sink is suchfacet coating “overspray.”

Lastly, as a final additional complexity of some commercially-mountedlaser diodes, as many as 6 to 12 microscopic gold wires are individuallyball-bonded onto the cathode surface of the laser diode, for the purposeof providing a return current path from the laser device.

From the foregoing, it will be appreciated that there has long been aneed for a method of mounting semiconductor devices such as laser diodesthat provides the desired thermal and optical performance while beingsimpler and more reliable to manufacture and assemble.

SUMMARY OF THE INVENTION

The present invention provides the aforementioned improvements byproviding apparata that are simpler to manufacture than the prior artwhile providing excellent heat conduction away from the semiconductordevice, and also providing optical performance similar to that achievedwith laser diodes soldered to a heatsink.

In an embodiment, the apparatus of the present invention comprises asandwich of a pair of partially compressible, thermally conductivegraphite sheets with a spacer therebetween. In the spacer is a slotessentially matched in size (length and width) to a laser diode, whichis positioned within the slot when the assembly is complete. In anembodiment, the spacer is equal to or slightly thinner than the heightof the semiconductor device, to ensure adequate contact between thegraphite sheets and the semiconductor. The graphite sheets are thencompressed by any suitable means into good thermal and electricalcontact with the laser diode, with the spacer preventing unduemechanical stress on the laser diode. Because the graphite sheet iscompressible and much softer than the spacer or the semiconductor,uniform modest pressure can be applied to the laser diode withoutbreaking the laser diode chip.

In an embodiment, the assembly is held together with screws and the“sandwich” of the cathode and anode plates are compressed by themechanical force of the screws. Alternatively, the assembly can be gluedtogether, for example using a UV-cured epoxy, in which case thecomponents are placed together and then suitably compressed in advanceof gluing, and held in compression until the glue is suitably cured orotherwise set. The glued embodiment is particularly well-suited toautomated assembly, although automated assembly is possible with manyother embodiments.

THE FIGURES

FIG. 1 illustrates in exploded view an embodiment of a device inaccordance with the invention.

FIG. 2 illustrates in exploded view an alternative embodiment of adevice in accordance with the invention.

FIG. 3 illustrates in cross-sectional side view an assembled version ofthe device shown in FIG. 2.

FIG. 4 illustrates an embodiment suitable for assembly by gluing.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an embodiment of a device in accordance with theinvention is shown in an exploded view. In such an embodiment, thedevice can be of generally rectangular shape, of dimensions nominally0.5 inch wide by 0.25 inch deep by 0.25 inch in thickness. It will beappreciated that these dimensions and shapes are exemplary only, and arelargely a matter of design choice. Thus, the dimensions and shapes shownand described herein are not intended to be limiting. For example, theentire device could be made much smaller by simply utilizing screwssmaller than the 0-80 size contemplated in the drawing, or by using glueas discussed in connection with the embodiment of FIG. 4. Similarly, theshape can be altered to any convenient form, as long as sufficientcompression is provided to ensure reliable mechanical placement as wellas thermal and electrical conductivity among the various components,together with sufficient heat removal.

In the embodiment shown in FIG. 1, a cathode block 10 is comprised of anelectrically and thermally conductive material such as copper or thelike. A pair of threaded holes 15 is positioned essentially near theouter perimeter of the block, although the particular location is notcritical, and other fastening mechanisms can be used. A first conductivesheet 20 is positioned above the cathode block 10, and a spacer 30 ispositioned above the sheet 20. The spacer 30 is electrically insulating,and preferably will be thermally conductive in at least someembodiments. Further, for some embodiments, it is desirable that thespacer have thermal conductivity of at least 50 watts per meter-degreeKelvin (50 W/m-deg K), which can be achieved with, for example, a coppersheet having a Mylar layer bonded thereto, or a copper sheet having atleast one of the top or bottom surfaces or coated with insulatingvarnish or polyurethane, or anodized aluminum, or aluminum coatedsimilarly to copper. In some embodiments where the spacer is metal witha single insulating layer such as Mylar, it may be desirable to placethe bare metal surface against the PGS sheet closest to the anode block.In general, the spacer will preferably have high thermal conductivity,ease of fabrication, and low cost. Thus, in other embodiments, athermally conductive plastic material, or composites with high thermalconductivity particles mixed in, or ceramic-like materials with goodthermal conductivity such as beryllium oxide or boron nitride, or othermetals combined with an insulating layer, can be acceptable for thespacer.

A slot 40 extends inwardly from the near edge of the spacer 30, and hasdimensions essentially intended to match laser diode 50, with thethickness of the spacer 30 substantially the same as the thickness, orheight, of the laser diode 50. The emitting facet 55 of the laser diodeis positioned at the open end of the slot, allowing laser light to exitthe edge-emitting device in the intended manner. In some embodiments,the laser diode 50 can comprise a bar having multiple stripes oremitters, for example two or three stripes, such that light is emittedfrom two or three locations.

A second conductive sheet 60 is positioned above the spacer 30 and laserdiode 50, when the laser diode is positioned within the slot 40. Ananode block 70 is positioned above the second conductive sheet 60. Theassembly can be clamped together by any convenient means, such aselectrically insulating shoulder washers 80 and electrically conductivebolts or screws 90, and for this purpose holes 95 are provided in eachof the conductive sheets and the spacer. As noted above, other fasteningapproaches can be used, such as glue, insulated spring clips or thelike. A pair of conductive lugs, not shown in FIG. 1 but visible in theassembly drawing of FIG. 3, provides appropriate electrical connectivityto the anode and cathode blocks.

In the embodiment of FIG. 1, the laser diode is effectively clampedbetween the anode block and cathode block by virtue of the screws orbolts 90. The conductive sheets 20 and 60 are somewhat compressible, andthus both hold the laser diode in place mechanically as well as formingelectrical contact with the laser diode uniformly along the length ofthe laser diode. An electrically conductive path is formed from theanode, through the first conductive sheet, then through the laser diode,the second conductive sheet, and finally the cathode block. The spacerprevents electrical conductivity except through the laser diode. Ifdesired, shims (not shown) can be provided between the anode and cathodeblocks, or integrated with the spacer 30, to prevent excessive clampingforce on the laser diode.

The conductive sheets 20 and 60 are preferably formed from pyrolytichighly oriented graphite sheet (sometimes “PGS” or “pyrolytic graphite”hereinafter) such as sold by Panasonic Electronic Devices Co., Ltd. Someformulations of such pyrolytic graphite sheets, such as those currentlysold by Panasonic, provide better thermal conductivity if compressed.Thus, in some embodiments, the sheets 20 and 60 are preferablycompressed about fifteen to thirty percent (nominally 25%) to ensuregood thermal conductivity, although the amount of compression can beadjusted over a wide range, from about five percent to about fortypercent, depending upon the embodiment and particularly the amount ofheat generated and the nature of the thermal pulse applied to the PGSmaterial. The thickness of the sheets 20 and 60 need not be the same(more heat is generated on the anode side of the laser diode). It shouldbe noted that the actual thermal conductivity of PGS material increasesas the sheet becomes thinner. Thus, for example, designs which generaterelatively more heat, and do so more quickly, may benefit fromrelatively thin sheets on the anode side, whereas a different thicknessmay be preferred for other designs using with different thermal pulseshapes. In general, a clamping force of approximately 6 kg/m² providesadequate compression for the embodiment described, although in otherimplementations a range of 1-30 kg/m² will be acceptable, with a rangeof 4-8 kg/m² generally preferred. In some embodiments, including thoseinvolving higher power or longer pulse duration, it may be desirable toreduce electrical contact resistance between the laser diode and the PGSmaterial, particularly on the anode side. For such embodiments, thesurface of the PGS material that contacts the light emitting device canbe plated by any convenient means, such as electroplating or vapordeposition, with a conductive material such as copper or gold. In otherembodiments, the surface that contacts the cathode side of the lightemitting device can also be coated, and, in still other embodiments,both top and bottom of the PGS material can be coated. The conductivematerial is preferably plated to a thickness of one to 25 microns, witha thickness of 5-10 microns being generally preferred. The metal layeron the PGS material is sufficiently thin that the PGS material remainscompliant with the associated block (anode or cathode) as well as thelight emitting device.

The sheets 20 and 60, made from such PGS material, offer lateral thermalconductivity (W/mK) ranging from 600 to 1800 for thicknesses rangingfrom 100 μm to 17 μm, respectively. Vertically, or in the Z direction,the thermal conductivity of such PGS material is about 15 W/mK, orroughly equivalent to the thermal conductivity of various solders aswould be used in a solder-mounting of laser diodes, with higherconductivity being preferred. Advantageously, it will be appreciatedthat, in the present invention, it is not necessary to have multi-layermetallized surfaces on the laser diode, as is generally required forsolder mounting. Instead, in at least some embodiments, the conductivesheets 20 and 60 can simply be placed in direct contact with anunmetallized laser diode to achieve proper current flow. The graphitematerial also has excellent electrical conductivity, comparable toindium, lead or tin. It should be noted, however, that the novel designof the invention described herein is not intended to be limited to theincorporation of pyrolytic graphite, but rather encompasses the use ofother very high thermal conductivity, compressible materials with goodelectrical conductivity as well.

The present invention is well-suited to applications requiring laserdiodes or diode bars operating in the range of 400 nm to 2000nanometers, with drive currents from 0.5 to 20 amperes, pulse durationsfrom one millisecond to one second, and duty factors as high as fiftypercent. In pulsed mode, the present invention can be operated in eithera single pulse mode or a repetitively pulsed mode. In an exemplaryembodiment, the device can be operated with five millisecond pulses at apulse repetition rate of 30 Hz, corresponding to a duty factor offifteen percent. For a drive current of ten amperes, the output power ofeach pulse is about four watts. For a pulse duration of about fivemilliseconds, this produces a pulse energy of about 30 millijoules. Insome embodiments, continuous operation can be used.

FIG. 2 illustrates an alternative, and presently preferred, embodimentwhere a single laser diode device is used. Elements substantiallysimilar to those in FIG. 1 are designated by like numerals.

In the embodiment of FIG. 2, cathode block 10 is typically machined outof copper, with a channel 25 milled at a convenient location, forexample, in its center, resulting in surfaces 35 on either side of thechannel 25. Channel 25 is machined to a depth such that, when surfaces35 contact the anode block 70, the PGS sheets 20 and 60 undergoapproximately 25% compression. This depth can be, for example, 10 mils,depending on the dimensions of the diode 50 and the thickness of the PGSsheets. At roughly 25% percent compression most of the thermalperformance of the PGS material is achieved, while providing sufficientclamping force both to ensure good electrical connection and to ensurethat the diode 50 does not move, while at the same time limiting thepressure on the diode 50 to avoid damage. In an embodiment, the clampingforce to provide appropriate compression of the sheets 20 and 60, and tofixedly clamp the laser diode or other semiconductor, can range fromabout 1-30 kg/m², although in most designs a range of 4-8 kg/m² will beacceptable. In some embodiments, surfaces 35 of the cathode block aresprayed with a few tenths of a mil of an electrically insulatingsubstance, such as common polyurethane. This avoids electrical shortingof the cathode block 10 to the anode block 70, and forces electricalcurrent to pass through the laser diode chip 50. In an alternativeembodiment, a thermally conductive but electrically insulating spacer 30(such as a copper sheet with a bonded Mylar layer) extends laterally tocover surfaces 35 of the cathode block shown in FIG. 2. This eliminatesthe need for spraying an electrically insulating layer directly ontothese surfaces of the cathode block.

For assembly, a piece of PGS material 20, for example of a thickness offour mils and dimensions of approximately ¼ inch by 3/16 inch, is placedin the channel 25. A spacer 30, equal in thickness to that of the laserdiode chip 50 (nominally 6 mils), is then placed on top of the PGS sheet20. A laser diode chip 50 is then placed in slot 40 of spacer 30. Laserdiode chip 50 is oriented such that its laser emission propagates outthrough emission facet 55 and out of the assembly when current isapplied. The chip 50 is also oriented such that the P-side is upward inthe figure, so that the laser stripe is facing toward the anode block 70for proper current flow.

A second sheet of PGS 60, approximately one mil thick, is then placed ontop of the chip 50 and spacer 30, followed by the anode block 70. Tocomplete the assembly, machine screws 90 are slid through insulatingshoulder washers 80 and then through thru-holes 95; and threaded intothreaded holes in the cathode block 10. Because of the innovative designof this compression mount assembly, the pressure on the laser diode chip50 is essentially independent of the torque applied to the machinescrews. That is, once surfaces 35 of the cathode block 10 press againstthe anode block 70, the total gap distance of channel 25 is essentiallyindependent of the torque applied to the machine screws, resulting insimple and reliable assembly, substantially the same as the shimsdiscussed in connection with FIG. 1.

To drive electrical current through the assembled compression mount, andmore particularly through the laser diode, reference is made to FIG. 3,which illustrates the same embodiment as shown in FIG. 2, but this timein cross-section. To make the anode electrical connection, machine screw90A is placed through insulating shoulder washer 80A, which in turnrests on anode ring lug 300 atop anode block 70. Anode ring lug 300 isthe termination of the electrical wire, and associated circuitry (notshown) providing current to the assembly. Because anode ring lug 300rests on anode block 70, electrical connection is made. Machine screw90A is then threaded into cathode block 100.

The return current path is formed in an analogous manner. Machine screw90C is placed through cathode ring lug 310, and then through insulatingshoulder washer 80C. Because machine screw 90C is threaded into cathodeblock 10 as well, the screw itself is at cathode potential, providing areturn current path through cathode ring lug 310 to the electrical wirereturning current from the assembly.

In testing, the embodiment described above in connection with FIG. 2,using a thermally conducting copper spacer coated with a thinelectrically insulating layer of polyurethane, offers laser light outputsubstantially equivalent to a conventional mounting (where a laser diodehas the P-side soldered to a gold-plated heat sink and has multipleindividual gold wire bonds to the N-side) for individual 5-millisecondpulses up to roughly 10 amperes. Similar equivalence has beendemonstrated when both devices are operated at significant average power(e.g., at a repetition rate of 30 Hz) for over ten minutes, confirmingthat the heat transfer from the present invention is equivalent to thatof conventional mounts for longer timescales as well. The indicatedperformance of the present invention offers significant utility. Forexample, in an embodiment suitable for use in a fractional non-ablativedevice, pulsed current in the range of four to eight amperes, having apulse duration of five milliseconds, provides an optical output energyof approximately seven to fifteen millijoules. Those skilled in the artwill recognize that both current and pulse duration can be varied toadjust the output as desired.

It is noted that the embodiment described herein is intended to serveonly as an example of the novel mounting scheme using compression; thereare many variations that would perform equally well, and may have theirown particular advantages. In one such variation, only one side of thelaser diode chip may utilize the pyrolytic graphite or similar material,with the other side rigidly attached. For example, the N-side of thelaser diode may be soldered to a copper trace on a conventional printedcircuit board. The thinness of the trace provides sufficient mechanicalcompliance to allow soldering of the chip to copper rather than anexpansion-matched copper-tungsten alloy. With the chip soldered to aprinted circuit board, other electronic components and/or sensors may belocated very close by using conventional PC-board assembly methods. Inanother embodiment, the P-side of the laser diode chip is placeddirectly in contact with a polished surface of the anode block; thegraphite material in contact with the cathode side of the chip providesthe requisite compressibility to avoid cracking the chip. In yet anotherembodiment, a channel is created in both the anode and cathode block toretain the graphite material conveniently. The channel depths arechosen, along with the thicknesses of the anode and cathode graphitematerials, such that the entire assembly, when compressed, compresseseach graphite sheet by approximately 25%.

The simplicity, reliability and ease of manufacture of the presentinvention make this device ideally suited for a high-volume consumerlaser device, such as a non-ablative fractional laser. Thecompression-mounting approach is equally applicable to so-called laserdiode bars, in which a plurality of emitters, frequently in the range of18-20, are located adjacent to each other, all emitting from the side ofthe diode bar. This type of bar, typically made of gallium arsenideoperating at a wavelength of about 800 nm, is used in consumer laserhair removal devices, although many other uses exist for devices usingdifferent wavelengths or different semiconductor devices. Many of theabove-stated benefits of the current invention are equally applicable tothese types of applications. In such an arrangement, the slot 40 issimply widened.

Referring next to FIG. 4, a further alternate embodiment is illustrated,wherein the entire assembly is glued together, rather than screwed orbolted together. In an embodiment, small pockets are formed in two orthree sides of the assembly where the anode and cathode blocks approacheach other (excluding the side emitting the laser light). Glue is theninserted into these pockets and cured, e.g., with a UV-curing cement, atwo-part epoxy, a cyanoacrylate-type of cement, etc. If the assembly isglued together, electrical connections can easily be made to the cathodeand anode blocks by standard means, such as solder (prior to assembly),for the inflow and outflow of electrical current. During the gluingprocess, the assembly is maintained under pressure such that the desiredamount of compression of the PGS sheets is achieved, and remains so oncethe glue has cured or set.

In particular, an anode block 400 is positioned above a cathode block405, with a spacer 410 positioned therebetween. A sheet of pyrolyticgraphite material 415 is positioned between the anode block 400 and thespacer 410, aligned with a channel 420 in the anode block 400.Similarly, a second sheet of pyrolytic graphite material 425 ispositioned between the spacer 410 and cathode block 405, aligned with achannel 430 in the cathode block. A slot 435 is placed in the spacer 410receives the light emitting device (not shown, see FIG. 2), with thethickness of the spacer the same as, or slightly thinner than, the lightemitting device, as discussed previously.

The elements shown in FIG. 4 are assembled by any convenient means. Forexample, the components can be aligned for assembly by mean of a fixturefor positioning the cathode block and remaining elements, and thencompressing the assembled components by clamping until the spacercontacts the anode and cathode plates. Glue can then be inserted intoglue pockets 440 and allowed to set or cure, at which time the clampingis removed. The configuration is otherwise substantially identical withthat shown in FIG. 2, including the options of plating the PGS materialto reduce electrical contact resistance, or using laser diodes havingmultiple emitters.

It will be appreciated from the teachings herein that the thickness ofthe sheets 415 and 425 can be of different thicknesses. For example, thesheet 425 on the cathode side can be approximately 100 microns thick,while the sheet 415 on the anode side can be approximately 25 micronsthick. For such thicknesses, the depth of channel 420 can beapproximately 17 microns, while the depth of the channel 430 can beapproximately 75 microns. Although the size of the cathode and anodeblocks is not critical, a workable size is approximately 1 cm×1 cm×0.5cm, with the sheets of pyrolytic graphite material roughly to scale. Thespacer is, as mentioned above, nominally a 5 mil thick copper sheet witha one mil layer of Mylar bonded thereto, and “pockets” nominally 125mils deep.

In an alternative embodiment, the channel in the anode block iseliminated, and the anode metallization of the light emitting deviceeither rests directly on the polished copper anode block, or rests on athin (˜17-25 micron) sheet of pyrolytic graphite material without achannel.

As discussed above, a laser diode utilizing a simple compressionassembly can enjoy excellent heat conduction away from its surfaceswithout the complexity and reliability issues associated with a solderedassembly, and without the need for specially prepared metallizationcoatings such as titanium, nickel and gold on the laser diode anode andcathode surfaces.

From the foregoing, it can be appreciated that a new, novel andinventive device, and method of manufacture of such device, has beendisclosed. From the foregoing teachings, those skilled in the art willrecognize that numerous alternatives and equivalents exist which do notdepart from the scope of the invention, and therefore the invention isintended to be limited only by the appended claims.

1. An apparatus for generating laser light comprising: electricallyconducting anode block, electrically conducting cathode block,semiconductor diode laser device having an anode and a cathode,positioned between the anode block and the cathode block; first layer ofelectrically conductive, highly thermally conductive, compressiblematerial positioned between the anode block and the anode of the laserdevice; an electrically insulating layer surrounding a portion of thesemiconductor device and disposed between the compressible material andthe cathode block to electrically isolate the anode block from thecathode block, means for maintaining compression of the compressiblematerial, maintaining electrical and thermal conduction between theanode of the laser device and the anode block through the compressiblelayer, and maintaining electrical and thermal conduction between thecathode side of the laser device and the cathode block.
 2. The apparatusof claim 1 wherein the compressible material is a form of pyrolyticgraphite sheet.
 3. The apparatus of claim 1 wherein the laser device ispulsed and has a pulse duration from one millisecond to one second, anda duty factor less than 50%.
 4. The apparatus of claim 1 wherein thelaser device has an output wavelength from 400 nm to 2,000 nm.
 5. Theapparatus of claim 1 wherein the anode and cathode blocks are thermallyconductive.
 6. The apparatus of claim 1 wherein the laser devicecomprises from one to three emitters.
 7. The apparatus of claim 2further comprising a second layer of pyrolytic graphite sheet positionedbetween the cathode of the laser device and the cathode block.
 8. Theapparatus of claim 2 wherein the means for maintaining compression isglue.
 9. The apparatus of claim 2 wherein the means for maintainingcompression is screws or bolts.
 10. The apparatus of claim 2 wherein themeans for maintaining compression is at least one spring clip.
 11. Theapparatus of claim 2 wherein the electrically insulating layer comprisesa thermally conductive spacer having a slot therein for receiving thelaser device, and being of substantially the same thickness as the laserdevice, the spacer being disposed around at least a portion of the sidesof the laser device.
 12. The apparatus of claim 11 wherein the spacer isone of a group comprising beryllium oxide, anodized aluminum, aluminumhaving an electrically insulating layer, and copper having anelectrically insulating layer.
 13. The apparatus of claim 1 wherein thecompressible material is plated with a material from a group comprisingat least copper and gold where the compressible material contacts theanode.
 14. Apparatus for removing heat from an edge-emittinglight-emitting semiconductor device comprising a thermally conductiveanode block, a thermally conductive cathode block, anelectrically-insulating, thermally conductive spacer having a slottherein for receiving an edge-emitting light emitting device, the slotbeing arranged to permit light from the light emitting device to exitthe apparatus, the light emitting device having an anode and a cathodeand placed in the slot so that the anode is closest to the anode blockand the cathode is closest to the cathode block, a first sheet ofpyrolytic highly-oriented graphite interposed between the anode blockand at least a portion of an area formed by a combination of the spacerand the anode, a second sheet of pyrolytic highly-oriented graphiteinterposed between the cathode block and at least a portion of an areaformed by a combination of the spacer and the cathode, means formaintaining compression of the pyrolytic highly-oriented graphite sheetsagainst the light emitting device to ensure thermal and electricalconductivity therebetween.
 15. The apparatus of claim 14 wherein thecompression of the graphite sheets is maintained at approximatelytwenty-five percent.
 16. The apparatus of claim 14 wherein the anodeblock and cathode block are glued together to maintain compression ofthe graphite sheets.
 17. The apparatus of claim 14 wherein the first andsecond sheets are of different thicknesses.
 18. The apparatus of claim14 wherein the spacer has a thermal conductivity of at least 50 W/m degK.
 19. Apparatus for removing heat from a semiconductor diode laserdevice comprising a thermally conductive anode block, a thermallyconductive cathode block, an electrically-insulating, thermallyconductive spacer having a slot therein for receiving a semiconductordiode laser device, the slot being arranged to permit light to from thelaser device to exit the apparatus, the laser device having an anode anda cathode and placed in the slot so that the anode is closest to theanode block and the cathode is closest to the cathode block, a firstsheet of pyrolytic highly-oriented graphite interposed between the anodeblock and at least a portion of an area formed by a combination of thespacer and the anode, glue to position the anode block sufficientlyproximate to the cathode block that the first sheet is maintainedcompressed about twenty-five percent.
 20. The apparatus of claim 19wherein the spacer comprises copper with an electrically insulatinglayer, and the insulating layer is closest to the cathode block.
 21. Theapparatus of claim 19 wherein the spacer has a thermal conductivity ofat least 50 W/m-deg K.
 22. The apparatus of claim 19 wherein the diodelaser device is pulsed with pulses having a pulse duration from onemillisecond to one second, and a duty factor less than 50%.
 23. Theapparatus of claim 22 wherein a second sheet of pyrolytichighly-oriented graphite is interposed between the cathode block and atleast a portion of an area formed by a combination of the spacer and thecathode.
 24. The apparatus of claim 19 wherein the first sheet is platedwith one of a group comprising copper and gold in an area where thefirst sheet contacts the anode.
 25. Apparatus for mounting asemiconductor laser diode device comprising a thermally and electricallyconductive anode block, a thermally and electrically conductive cathodeblock, an electrically-insulating spacer having a thermal conductivityof at least 50 W/m-degK, and further having a slot therein for receivinga semiconductor laser diode device having an output wavelength between400 nm and 2000 nm and operating in pulsed mode with pulses between onemillisecond and one second at a duty factor less than fifty percent, theslot being arranged to permit light from the laser diode device to exitthe apparatus, the laser diode device having an anode and a cathode andplaced in the slot so that the anode is closest to the anode block andthe cathode is closest to the cathode block, a first sheet of pyrolytichighly-oriented graphite interposed between the anode block and at leasta portion of an area formed by a combination of the spacer and theanode, a second sheet of pyrolytic highly-oriented graphite interposedbetween the cathode block and at least a portion of an area formed by acombination of the spacer and the cathode, means for maintainingcompression of the pyrolytic highly-oriented graphite sheets against thelight emitting device to ensure thermal and electrical conductivitytherebetween.
 26. The apparatus of claim 25 wherein the spacer comprisescopper and an electrically insulating layer, and the electricallyinsulating layer is positioned proximate to the cathode block.
 27. Theapparatus of claim 25 wherein the first sheet is thinner than the secondsheet.
 28. The apparatus of claim 25 wherein the duty factor does notexceed twenty percent.
 29. The apparatus of claim 28 wherein the firstsheet is plated with a metal in an area where the first sheet contactsthe anode.
 30. The apparatus of claim 14 wherein channels are formed inthe anode block and cathode block for receiving the first and secondsheets.